Method and apparatus for plating a semiconductor package

ABSTRACT

A method of plating a plurality of semiconductor devices includes: applying an electrical power source to an anode terminal and a cathode terminal; placing the plurality of semiconductor devices on a non-conductive platform in a plating solution; moving conductive parts across surfaces of the semiconductor devices to be plated, wherein the conductive parts electrically connect the surfaces of the semiconductor devices to the cathode; and wherein plating particles connected to the anode terminal move to and plate the surfaces of the semiconductor devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 12/128,828 filed on May 29, 2008, which claims priority from U.S.Provisional Application No. 60/940,824 filed on May 30, 2007, thedisclosure of which is incorporated herein by reference.

BACKGROUND OF INVENTION

1. Field of Invention

Apparatuses and methods consistent with the present invention relate toa method of electro-plating a semiconductor packages. More particularly,the present invention relates to a apparatus and method ofelectro-plating singulated semiconductor packages by moving conductiveparts and the singulated packages relative to each other.

2. Description of the Related Art

One of the last steps in manufacturing certain types of semiconductorpackages, such as QFN packages, is to plate the metal frame with aconductor, such as solder. One such conventional method is toelectro-plate a metal, such as solder, to the frame. FIG. 1 is aschematic view of a conventional method of electro-plating a strip ofsemiconductor packages. The electro-plating apparatus includes acontainer 1 that is filled with a plating chemical 2, such as MethaneSulfonic acid. An electrical power source 3 is connected to an anode 3 aand a cathode 3 b. The anode 3 a is electrically connected to an anodeplate 4 that contains solder particles. The cathode 3 b is electricallyconnected to a clipper and belt that is attached to the metal frame 6 ofthe semiconductor packages to be plated. The apparatus also includes acirculation pump and filter 7, which circulates the chemical in order toprevent chemical debris sediment.

When an electrical current is applied by the electrical power sourcethrough the anode 3 a and cathode 3 b to the anode plate 4 and metalframe 6, the solder particles on the anode plate move (as shown by item8) through the plating chemical and become plated onto the metal frame(as shown by item 9).

FIG. 2 illustrates differences between the conventional strip ofsemiconductor packages and the strip of semiconductor packages that isused in an embodiment of the inventive method. FIG. 2A shows a portionof a metal strip frame 10 that contains rail bars 11, tie bars 12,terminals 13 and die attach pads 14. Each of the rail bars 11, tie bars12, terminals 13 and die attach pads 14 are electrically connected. As aresult, all of the metal surfaces can be plated by the conventionalmethod.

FIG. 2 b shows what happens with individual semiconductor packages aresingulated, or separated from each other. Specifically, the rail barsare cut. After singulation, the tie bars 12, terminals 13 and die attachpads 14 of each of the singulated packages are no longer electricallyconnected to the tie bars 12, terminals 13 and die attach pads 14 of theother singulated packages. As a result, because electric current can nolonger flow through all of the metal parts, the parts cannot be electroplated.

While the conventional method works well for semiconductors packages ona strip, when the semiconductor packages are singulated prior toelectro-plating, a new method is necessary. The need to electro-plateindividual packages may arise when not all of the packages on a stripare properly plated during the conventional method. Rather thanscrapping the unplated packages, they can be separated from the stripand plated in a separate process.

There is therefore a need to provide apparatuses and methods that canelectro plate semiconductor packages that have been singulated.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention overcome the abovedisadvantages and other disadvantages not described above. Also, thepresent invention is not required to overcome the disadvantagesdescribed above, and an exemplary embodiment of the present inventionmay not overcome any of the problems described above.

In one embodiment a method of plating a plurality of semiconductordevices includes: applying an electrical power source to an anodeterminal and a cathode terminal; placing the plurality of semiconductordevices on a non-conductive platform in a plating solution; movingconductive parts across surfaces of the semiconductor devices to beplated, wherein the conductive parts electrically connect the surfacesof the semiconductor devices to the cathode; and wherein platingparticles connected to the anode terminal move to and plate the surfacesof the semiconductor devices.

In other embodiments of the above method, the plurality of semiconductordevices are not electrically connected, the conductive parts are shapedas one of spheres, cylinders, polyhedrons, brushes, pins, wheels andhairs, and/or the conductive parts move in a circular direction.

In another embodiment, a method of plating a plurality of semiconductordevices includes: applying an electrical power source to an anodeterminal and a cathode terminal; placing the plurality of semiconductordevices on a non-conductive platform in a plating solution; movingsurfaces of the semiconductor devices to be plated across conductiveparts, wherein the conductive parts electrically connect the surfaces ofthe semiconductor devices to the cathode; and wherein plating particlesconnected to the anode terminal move to and plate the surfaces of thesemiconductor devices.

In other embodiments of the above method, the plurality of semiconductordevices are not electrically connected and/or the conductive parts areshaped as one of brushes, pins, wheels and hairs.

In another embodiment, a method of plating a plurality of semiconductordevices includes: applying an electrical power source to an anodeterminal and a cathode terminal; placing the plurality of semiconductordevices, which may or may not be electrically connected, on anon-conductive platform in a plating solution; moving conductive partsacross surfaces of the semiconductor devices to be plated in a firstdirection, wherein the semiconductor parts are moving in directionopposite to the first direction, wherein the conductive partselectrically connect the surfaces of the semiconductor devices to thecathode; wherein plating particles connected to the anode terminal moveto and plate the surfaces of said semiconductor devices.

In other embodiments of the above method, the conductive parts areshaped as one of spheres, cylinders, polyhedrons, brushes, pins, wheelsand hairs, and/or the conductive parts move in a circular direction.

In another embodiment, an apparatus for plating a plurality ofsemiconductor devices includes: a container for holding a platingchemical; an electrical power source connected to an anode terminal anda cathode terminal; a container for holding plating particles connectedto the anode terminal; a non-conductive platform for holding theplurality of semiconductor devices, which may or may not be electricallyconnected; and movable conductive parts that electrically connectsurfaces of the semiconductor devices to be plated to the cathodeterminal.

In other embodiments of the above apparatus, the apparatus alsoincludes: a conductive enclosure, which may be a ring; a conductiveplate; and a conductive support; wherein the conductive enclosure, theconductive plate and the conductive support are electrically connectedto said cathode terminal and wherein the conductive enclosure providesthe electrical connection between the movable conductive parts and thesurfaces of the semiconductor devices to be plated to the cathodeterminal.

In other embodiments of the above apparatus, the apparatus includes astirrer that moves the conductive parts across the surfaces of saidsemiconductor devices, and/or the conductive parts may be shaped as oneof spheres, cylinders, polyhedrons, brushes pins, wheels and hairs.

In another embodiment, an apparatus for plating a plurality ofsemiconductor devices includes: a container for holding a platingchemical; an electrical power source connected to an anode terminal anda cathode terminal; a container for holding plating particles connectedto the anode terminal; a movable non-conductive platform for holding theplurality of semiconductor devices, which may or may not be electricallyconnected; and conductive parts that electrically connect surfaces ofthe semiconductor devices to be plated to said cathode terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the present invention will becomeapparent and more readily appreciated from the following description ofthe exemplary embodiments, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a schematic view of a conventional method ofelectro-plating a strip of semiconductor packages.

FIG. 2 illustrates differences between the conventional strip ofsemiconductor packages and the strip of semiconductor packages used inan embodiment of the inventive method.

FIG. 3 illustrates a schematic view of an embodiment of the inventivemethod and apparatus.

FIG. 4 illustrates a top view of an embodiment of the inventive methodand apparatus.

FIG. 5 illustrates a bottom view of an embodiment of the inventivemethod and apparatus.

FIG. 6 illustrates a partial side view of an embodiment of the inventivemethod and apparatus.

FIG. 7 illustrates a partial perspective view of an embodiment of theinventive method and apparatus.

FIG. 8 is a table of visual inspection test results of an embodiment ofthe inventive method.

FIG. 9 is a table of adhesion test results of an embodiment of theinventive method.

FIG. 10 is a table of solderability test conditions related to anembodiment of the inventive method.

FIG. 11 is a table of solderability test results of an embodiment of theinventive method.

FIG. 12 is a photograph of the unit related to an embodiment of theinventive method.

FIGS. 13 are 14 are photograph of whisker test results related to anembodiment of the inventive method.

FIGS. 15A and 15B illustrate partial top views of embodiments of theinventive method and apparatus.

FIG. 16 illustrates different embodiments of the conductive parts.

FIGS. 17 and 18 illustrate an alternate embodiment of a stirrer blade ofthe inventive method and apparatus.

FIG. 19 illustrates an alternate embodiment of a stirrer blade of theinventive method and apparatus.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings.

FIGS. 3-6 illustrate schematic views of an embodiment of the inventivemethod and apparatus. The apparatus includes a container 20 that isfilled with a plating chemical 21, such as Methane Sulfonic acid. Thecontainer 20 can be made of Poly Propylene. An electrical power source22 is connected to an anode 22 a and a cathode 22 b. An example of anelectrical power source 22 is a source that outputs 2-3 Volts with acurrent of approximately 15 Amperes. The anode 22 a is electricallyconnected to a metal basket 29 that contains metal particles, such assolder balls. The cathode 22 b is electrically connected to a conductivecolumn 25. The conductive column 25 is electrically connected to aconductive bar 24, on which sits a conductive ring 31. Inside theconductive ring 31 and on top of the conductive bar 24 sits anon-conductive disk 34, which can be made of polyethylene. The apparatusalso includes a circulation pump and filter 23, which circulates thechemical in order to prevent chemical debris sediment.

The apparatus also includes an agitator 26, which is connected to abuffer unit 28 by an agitator axle 27. The buffer unit 28 contains astirrer blade 35 which is driven by the agitator 26, which acts as astirrer. FIG. 4, which is a top view of an embodiment of the apparatus,shows singulated semiconductor packages 36 fixed on a fixture 34 byusing, for example, UV tape to fix the unit to fixture 34 with thesurface to be plated facing up. The fixture is placed on thenon-conductive disk 34. A plurality of conductive parts are then placedinside the conductive ring and on top of the singulated semiconductorpackages 36. Typically, enough conductive parts are used so that thereare no gaps along the length of stirrer blade 35.

Next, the operation of the apparatus will be described. First, theagitator 26 is turned on, which causes stirrer blade 35 to rotate indirection 33 inside the conductive ring 31 at a rate of approximately15-20 RPM. The rotating stirrer blade 35 equally spreads the conductiveparts 32 over the singulated semiconductor packages. As the conductiveparts 32 move about inside the conductive ring 31, they are inelectrical contact with both the conductive ring 31 and the metalsurfaces of the singulated semiconductor packages. As a result, afterthe electrical power source 22 is turned on, electrical current isapplied by the electrical power source through the cathode 22 b,conductive column 25, conductive bar 24, conductive ring 31 andconductive parts to the metal surfaces of the singulated semiconductorpackages. The electrical power source 22 also applies electrical currentthrough the anode 22 a to the metal baskets 29 that contain metalparticles, such as solder balls. The metal particles in the metalbaskets then move through the plating chemical and become plated ontothe metal surfaces of the singulated semiconductor packages.

FIGS. 6 and 7 show other views of how the conductive parts 32 are usedin the embodiment. In order to create a uniform plating result, theconductive parts 32 are spread out evenly on the singulated units. Theconductive parts 32 conduct the electric current over the plating areawhich behaves as the cathode. The metal particles, which are driven byan electric field, travel from the metal baskets 29 (anode) to thecathode plating area.

Numerous reliability tests were performed to test the plating method.The results, discussed below, demonstrated that the plating method wasjust as reliable as conventional plating methods.

FIG. 8 is a table of visual inspection test results of the inventivemethod. Five lots were inspected, and none were rejected.

FIG. 9 is a table of adhesion test results of the inventive method.Again, five lots were tested, and none were rejected.

FIG. 10 is a table of solderability test conditions that were used totest the inventive method. FIG. 11 is a table of the solderability testresults that were obtained. Five lots were inspected, and none wererejected.

FIG. 12 is a photograph of the completed unit related to an embodimentof the inventive method.

FIGS. 13 are 14 are photograph of whisker test results related to anembodiment of the inventive method. A whisker is a defect that can occurduring a solder electroplating process.

The embodiment shown in FIGS. 3-7 are only one example of the inventivemethod. For example, the conductive parts, which are shown as spheres inFIG. 3-7, could also be shaped as cylinders, polyhedrons, etc., or acombination thereof, as shown for example in FIG. 16. In addition, theconductive parts could be hairs, pins, brushes, wheels, etc. that areattached to the stirrer blade. For example FIGS. 17 and 18 which show abrush-like stirrer blade 35 with hairs/pins 37. In addition, differenttypes of conductive parts can used together. For example, FIG. 19 showsa brush-like stirrer blade 35/37 used in combination with conductivespheres 32.

In another embodiment of the inventive method and apparatus, the stirrerblade and conductive parts can remain stationary while the semiconductorpackages rotate as shown in FIG. 15A. For example, conductive ring 31would be attached to the non-conductive disk 34, on which thesemiconductor packages 36 are fixed. The agitator would then be attachedto conductive ring 31. The agitator would then rotate conductive ring31, non-conductive disk 34 and semiconductor packages 36 together.

In another embodiment of the inventive method and apparatus, both thestirrer blade/conductive parts and semiconductor packages move, as shownfor example in FIG. 15B. This embodiment would require an additionalagitator that is attached to conductive ring 31. Also, like the previousembodiment, conductive ring 31 would be attached to the non-conductivedisk 34, on which the semiconductor packages 36 are fixed.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. An apparatus for plating a plurality of semiconductor devicescomprising: a container for holding a plating chemical; an electricalpower source connected to an anode terminal and a cathode terminal; acontainer for holding plating particles connected to said anodeterminal; a non-conductive platform for holding said plurality ofsemiconductor devices; and movable conductive parts that electricallyconnect surfaces of said semiconductor devices to be plated to saidcathode terminal.
 2. The apparatus of claim 1, further comprising: aconductive enclosure; a conductive plate; and a conductive support;wherein said conductive enclosure, said conductive plate and saidconductive support are electrically connected to said cathode terminaland wherein said conductive enclosure provides said electricalconnection between said movable conductive parts and said surfaces ofsaid semiconductor devices to be plated to said cathode terminal.
 3. Theapparatus of claim 2, wherein said conductive enclosure is a ring. 4.The apparatus of claim 2, further comprising: a stirrer that moves saidconductive parts across said surfaces of said semiconductor devices. 5.The apparatus of claim 2, wherein said conductive parts are shaped asone of spheres, cylinders, polyhedrons, brushes pins, and hairs.
 6. Theapparatus of claim 1, wherein said plurality of semiconductor devicesare not electrically connected.
 7. An apparatus for plating a pluralityof semiconductor devices comprising: a container for holding a platingchemical; an electrical power source connected to an anode terminal anda cathode terminal; a container for holding plating particles connectedto said anode terminal; a movable non-conductive platform for holdingsaid plurality of semiconductor devices; and conductive parts thatelectrically connect surfaces of said semiconductor devices to be platedto said cathode terminal.
 8. The apparatus of claim 7, wherein saidplurality of semiconductor devices are not electrically connected.